The present invention relates to the field of mass storage devices. More particularly, this invention relates to an actuator assembly in a disc drive.
One key component of any computer system is a device to store data. Computer systems have many different places where data can be stored. One common place for storing massive amounts of data in a computer system is on a disc drive. The most basic parts of a disc drive are a disc that is rotated, an actuator that moves a transducer to various locations over the disc, and electrical circuitry that is used to write and read data to and from the disc. The disc drive also includes circuitry for encoding data so that it can be successfully retrieved and written to the disc surface. A microprocessor controls most of the operations of the disc drive as well as passing the data back to the requesting computer and taking data from a requesting computer for storing to the disc.
The transducer is typically placed on a small ceramic block, also referred to as a slider, that is aerodynamically designed so that it flies over the disc. The slider is passed over the disc in a transducing relationship with the disc. Most sliders have an air-bearing surface (xe2x80x9cABSxe2x80x9d) which includes rails and a cavity between the rails. When the disc rotates, air is dragged between the rails and the disc surface causing pressure, which forces the head away from the disc. At the same time, the air rushing past the cavity or depression in the air bearing surface produces a negative pressure area. The negative pressure or suction counteracts the pressure produced at the rails. The slider is also attached to a load spring which produces a force on the slider directed toward the disc surface. The various forces equilibrate so the slider flies over the surface of the disc at a particular desired fly height. The fly height is the distance between the disc surface and the transducing head, which is typically the thickness of the air lubrication film. This film eliminates the friction and resulting wear that would occur if the transducing head and disc were in mechanical contact during disc rotation. In some disc drives, the slider passes through a layer of lubricant rather than flying over the surface of the disc.
Information representative of data is stored on the surface of the storage disc. Disc drive systems read and write information stored on tracks on storage discs. Transducers, in the form of read/write heads attached to the sliders, located on both sides of the storage disc, read and write information on the storage discs when the transducers are accurately positioned over one of the designated tracks on the surface of the storage disc. The transducer is also said to be moved to a target track. As the storage disc spins and the read/write head is accurately positioned above a target track, the read/write head can store data onto a track by writing information representative of data onto the storage disc. Similarly, reading data on a storage disc is accomplished by positioning the read/write head above a target track and reading the stored material on the storage disc. To write on or read from different tracks, the read/write head is moved radially across the tracks to a selected target track. The data is divided or grouped together on the tracks. In some disc drives, the tracks are a multiplicity of concentric circular tracks. In other disc drives, a continuous spiral is one track on one side of a disc drive. Servo feedback information is used to accurately locate the transducer. The actuator assembly is moved to the required position and held very accurately during a read or write operation using the servo information.
The read and write functionality of some disk drives is sometimes implemented using multiple movable mill-actuator arms mounted on one E-Block actuator arm. While other implementations of the read and write capability include a single moveable milli-actuator arm attached on the E-Block actuator arm. However, there can be undesirable performance problems when using the multiple movable milli-actuator design. When using multiple milli-actuator arms, one might expect to observe some manifestation of an interactive reaction of one milli-actuator on the other during seek operations. The problem confronting the industry is that this interaction can be detrimental to the operation of the disk drive, particularly when one milli-actuator is returning back to its zero position while the other milli-actuator is commanded to seek to a position. This degradation in operation can manifest itself as actuators experiencing seek errors or disturbances while on data tracks, and if the power supply capability is limited then drive operation can be impaired by the dual current draw demand.
What is needed is a disk drive configuration that not only minimizes milli-actuator reactive impulse but also provides a solution to excessive power current demands in disc drives using multiple moveable milli-actuator arms.
A method for minimizing the reactive impulse on a milli-actuator arm and relaxing the current demand on a power supply is disclosed. The method includes mounting several milli-actuator arms on a single E-Block actuator arm or a single actuator assembly. The method also includes causing a first movable milli-actuator arm to seek to a predetermined track position. Then a second movable milli-actuator arm is commanded to seek to a predetermined track position. The method further includes commanding a first movable milli-actuator arm to a rest position. The first movable actuator arm is commanded to return at a speed less than the speed of the second milli-actuator arm, when that second movable milli-actuator arm is seeking.
An information handling system is also disclosed. The information handling system includes a base, a disc rotatably attached to the base, and an actuator assembly movably attached to the base. The actuator assembly includes a voice coil attached to the actuator assembly. The information handling system further includes at least one magnet attached to the base and positioned near the voice coil to form a voice coil motor. The information handling system includes a system for commanding a first movable milli-actuator arm to return to a rest position at a reduced speed with respect to a second movable actuator arm when that second movable milli-actuator arm is commanded to seek. The information handling system also includes a processor for commanding the second movable milli-actuator arm to seek to a predetermined track position, wherein the second can be commanded to seek while the first movable milli-actuator arm is not at a rest position.
A disc drive is also disclosed. It includes a base, a disc rotatably attached to the base, an actuator attached to the base, one end of the actuator having a transducer and the other end of the actuator having a voice coil which forms a portion of a voice coil motor. The actuator includes a first rotatable portion, a second rotatable portion. The disc drive further includes a disc drive control circuit which includes a first rate of movement control circuit. The first rate of movement control circuit drives the first rotatable portion of the actuator at a different rate than the second rotatable portion. A second rate of movement control circuit drives the second rotatable portion of the actuator at a predetermined speed.
Advantageously, this invention has several features that can be useful in the application of mass storage device technologies. For example, by causing a first milli-actuator to return to a rest position at a reduced rate, with respect to the second seeking milli-actuator, improves the quality of operation by minimizing the reactive energy and thereby the disturbance to the seeking milli-actuator. Another advantage the present invention offers is an apparatus for simultaneously moving multiple milli-actuators and allowing them to be powered by a single, limited power supply. This reduces the degradation in the disc operation, which is often observed in such dual current draw scenarios. Furthermore, the present invention discloses circuitry that can drive the milli-actuators such that they travel in such a way as to exhibit the desirable characteristics discussed above. The circuitry according to the present invention also affords the circuit designer flexibility in their design.